For example, a railroad crossing gate control operation performed in a current railway transportation system will be described hereinbelow.
When a train is detected by a train detection device that is provided at an approach detection point which is established at a predetermined place before a railroad crossing, a warning device starts sounding, and after a lapse of a predetermined time period since a sounding start point of time, a gate arm of a railroad crossing gate is caused to descend, as illustrated in FIG. 1. Thereafter, when it is detected that the train having entered the railroad crossing leaves there, the sounding operation of the warning device is stopped and moreover, the gate arm is caused to ascend.
Incidentally, a time period T.sub.X between a moment from when the gate arm starts descending until the train enters the railroad crossing, should be secured as, for example, a time period required for an automobile or the like left in the railroad crossing to get out there, and should be equal to or longer than a predetermined time period (of, for instance, 15 seconds). Additionally, the sounding operation of the warning device, which is performed to inform an automobile or the like traversing the railroad crossing of the fact that the train approaches the railroad crossing, should be commenced a predetermined time (T.sub.0 shown in this figure, which is, for example, 30 seconds) or more before a train enters the railroad crossing.
Hitherto, for the purpose of securing the aforementioned time periods T.sub.X and T.sub.0, the timing with which the sounding operation of the warning device is started (namely, the timing with which a crossing inhibition command is issued) is controlled on the assumption that, among trains passing through the railroad crossing, the fastest one passes therethrough.
However, there are various kinds of trains, which run through a same running section, from a high-speed express train to a low-speed freight train. Thus, if the sounding operation is started with the same timing by assuming that, among trains passing through a railroad crossing, the fastest one passes therethrough, in the case that a train of which speed is lower than that of the assumed train, passes through the railroad crossing, it takes time, which is longer than required, until the train reaches the railroad crossing after the sounding operation of the warning device is started, or after the gate arm descends. Consequently, the aforementioned time periods T.sub.0 and T.sub.X become extremely long, so that a time period, during which automobiles and passers-by are prohibited from traversing the railroad crossing, becomes longer than required.
To solve the aforesaid problems, there has been employed a railroad crossing gate control operation that is referred to as a constant time control operation of timing-controlling in such a manner that the lengths of the time periods T.sub.0 and T.sub.X are constant (see, for instance, Yoshimura and Yoshikosi, "Signal", Koyusha, 1958).
A method for performing a constant time control operation is a delayed control method by which kinds of trains such as an express, a local train and a freight train is detected and then, if a train is of the kind that runs at a low speed, the sounding operation of the warning device and the operation of the gate arm are delayed.
However, in the case of employing such a delayed control method, when a train which usually travels at a high speed, runs by reducing the travelling speed thereof owing to an occurrence of a trouble over train operations, a sounding time period, during which the warning device sounds, and a railroad crossing closing time period, during which the railroad crossing is closed by the crossing gate, become long, similarly as in the aforementioned case. Further, trains assigned to the kinds of low-speed trains, for example, a freight train should run at a speed, which is lower than a speed limit, after passing through the approach detection point (namely, the train detection point), even in the case where the freight transported by the train is light and the train is thus in the condition that the travelling speed thereof can be easily increased. Moreover, the delayed control method requires troublesome operations of allocating the kinds to each train and of managing data representing the allocated kind.
Moreover, there has been employed a control method, by which the travelling speed of a train is detected at an approach detection point and the timing is controlled on the basis of the speed detected at that time, as another method of performing a constant time control operation. In this case, the troublesome operations for managing the allocated kinds of trains are unnecessary.
However, in the case of this method, if the train is accelerated after passing the approach detection point, the time periods T.sub.0 and T.sub.X are shortened. Thus, there are still restraints imposed on the speed at which the train runs after passing through the approach detection point.
As above stated, conventional railroad crossing gate control systems have various defects which should be improved in various respects.
Furthermore, in the case of managing train traffic, a track is partitioned into a plurality of sections. Then, the presence/absence of a train is detected in each of the sections. Subsequently, the entrance of the train into each of the sections and the leaving thereof from each of the sections are controlled. In such a train traffic management control system, a tracking circuit is employed as a conventional train detection device for detecting the presence/absence of a train in each of the sections.
Principle of the train detection performed by using such a track circuit will be described hereinbelow.
In each of a plurality of sections (referred to as a block section) obtained by partitioning a track, on which a train travels, thereinto, a power supply for feeding a signal current to be used to detect a train is connected to a pair of rails at the terminating side (namely, at the side from which the train leaves), while a track relay to be excited and driven by the aforementioned signal current is connected to a pair of rails at the beginning side (namely, at the side into which the train comes). Thus, a closed circuit for driving the track relay is constituted by utilizing a pair of rails as a part of an energizing path.
In such a constitution, when no train is present in a block section, electric current flows through the aforementioned closed circuit, so that the track relay is exited (thus, is raised) and an output signal indicating the absence of a train is generated as a result of a relay contact operation. In contrast, when the train enters the block section, wheels provide a short circuit between a pair of rails. Thus, electric current does not reach the track relay provided at the beginning side of the block section, so that the track relay is in a non-excited condition (thus, falls) and an output signal indicating the presence of a train is produced as a result of a relay contact operation. In this way, the presence/absence of a train is detected correspondingly to each of the block sections.
However, the conventional train detecting system, in which a train is detected by a track circuit utilizing the aforementioned electric circuit, has encountered a problem in that, although this system can detect whether or not a train is present in a block section, the system cannot specify a place, at which the train is present, in the block section.
Additionally, it is important for achieving a safe running operation of a train in a railroad transportation system to detect whether or not there is a rupture in rails.
There have been provided conventional devices for detecting a rupture in rails, an example of which will be described hereinafter.
Namely, a rail is insulated at predetermined intervals. Therefore, in a segment between insulated parts thereof, a transmitter is provided at an end portion thereof and a receiver is provided at the other end portion thereof. Thus, an electric current path is formed by utilizing the non-insulated segment of the rail. Further, if rupture takes place in the rail and portions of the rail are separated at a rupture part from one another, no electric current sent from the transmitter is transmitted to the receiver through a segment of the rail. Consequently, the device is adapted so that the presence/absence of a rupture in the rail is checked according to whether or not electric current supplied from the transmitter is transmitted to the receiver.
However, although the rupture occurring in the rail can be reliably detected by the conventional device in the aforementioned case of the ruptured condition in which the portions of the rail are separated at the rupture from one another, an electric current fed from the transmitter is allowed to flow through a part, which is not completely broken off, and can be received by the receiver according to the conventional method in the case that the rail is not completely ruptured but the portions thereof are partly connected at the rupture with each other. Moreover, in the case that the portions of the rail are in contact with each other even if the rail is completely ruptured, an electric current flows through the portions thereof can be received by the receiver. Consequently, the conventional rupture detection system has faced a problem in that this conventional system can detect only a condition where the rail is ruptured to the extent that the portions, into which the rail is divided at the rupture, are completely separated from one another.
In recent years, there have been demands for high-speed and high-density transportation in the railroad transportation system, with the intention of enhancing the efficiency in carrying passengers. Moreover, it has been requested that the aforementioned problems in respect of the railroad crossing gate control system, the train detection or the rail rupture detection are solved by simultaneously securing the higher safety and reliability than ever.
The present invention is accomplished in view of the aforesaid circumstances and aims at solving the aforementioned problems by transmitting and receiving elastic waves through a movement path of a mobile unit as a transmission medium and by generating information to be used for controlling/monitoring associated elements of a control system for performing control operations on the mobile unit, such as a railroad crossing gate control operation, a train detection operation or an operation of detecting an occurrence of rupture in the movement path, based on an elastic wave reception signal.